Direct measurement of carbon enrichment in the incomplete bainite transformation in Mo added low carbon steels

Yuan, Xiaoyan; Miyamoto, Gorō; Yang, Zhi; Zhang, Chao; Furuhara, Tadashi

doi:10.1016/j.actamat.2015.03.021

Cited by 67 publications

(27 citation statements)

References 26 publications

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“…Bainitic transformation has a characteristic of incomplete transformation (ICT) [13], in which reaction stops prematurely before the equilibrium amount is attained. The nature of ICT phenomenon could be explained by the concept of the T 0 curve [14,15], which places strict limits on the maximum fraction of transformation that can be achieved theoretically. In fact, both theoretical calculation and experimental results have proven that a lower transformation temperature can lead to an increase of bainite formation [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Zou

et al. 2019

Metals

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Both ausforming and transformation temperature affect the successive bainitic transformation and microstructure. The individual influence of each case is clear, whereas the combined effects are still unknown. Thermomechanical simulation and metallography were used to investigate the combined effects of ausforming and transformation temperature on bainitic transformation and microstructure. The kinetics of isothermal bainitic transformation in non-deformed and deformed materials was analyzed. A lower transformation temperature can lead to more bainite formation without deformation. However, ausforming with small strains can partially compensate for the decrease of bainite amount caused by the decreased undercooling. The larger the applied strain is, the smaller the difference between the final amounts of bainite with different undercooling. Ausforming at a relatively higher temperature is more favorable to the acceleration of subsequent isothermal bainitic transformation. The results in the present work provide reference for optimizing the fabrication technology of medium-carbon nanobainite steels.

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Section: Introductionmentioning

confidence: 99%

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Zou

et al. 2019

Metals

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“…As the Bs point decreases, the parent austenite transforms into LB at a low transformation temperature. In addition, a phenomenon called "incomplete transformation" usually occurs because bainite transformation stops prematurely before the equilibrium amount is attained [18,19]. Thus, residual austenite after bainite transformation partially transforms to martensite.…”

Section: Characteristics Of Microstructurementioning

confidence: 99%

Effect of Mo Content on Microstructure and Property of Low-Carbon Bainitic Steels

Zhou

et al. 2016

Metals

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Abstract:In this work, three low-carbon bainitic steels, with different Mo contents, were designed to investigate the effects of Mo addition on microstructure and mechanical properties. Two-step cooling, i.e., initial accelerated cooling and subsequent slow cooling, was used to obtain the desired bainite microstructure. The results show that the product of strength and elongation first increases and then shows no significant change with increasing Mo. Compared with Mo-free steel, bainite in the Mo-containing steel tends to have a lath-like morphology due to a decrease in the bainitic transformation temperature. More martensite transformation occurs with the increasing Mo, resulting in greater hardness of the steel. Both the strength and elongation of the steel can be enhanced by Mo addition; however, the elongation may decrease with a further increase in Mo. From a practical viewpoint, the content of Mo could be~0.14 wt. % for the composition design of low-carbon bainitic steels in the present work. To be noted, an optimal scheme may need to consider other situations such as the role of sheet thickness, toughness behavior and so on, which could require changes in the chemistry. Nevertheless, these results provide a reference for the composition design and processing method of low-carbon bainitic steels.

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“…In Fe-C-Mn-Mo system, the incomplete transformation was already observed in previous studies [38,39]. Xia et al [38] showed that adding 0.3Mo to a Fe-0.1C-1.5Mn (%wt) induced a transformation stasis at 550-600 • C but not at 500 • C where Mo showed no effect on the plateau of transformation. They also showed that adding Mo could affect the kinetics by retarding the transformation.…”

Section: Effect Of Mn and Mo On Ferrite Growth Kineticsmentioning

confidence: 58%

“…In austenite-to-ferrite phase transformation, this effect is known as coupled solute drag effect [22,23]. In Fe-C-Mn-Mo system, the incomplete transformation was already observed in previous studies [38,39]. Xia et al [38] showed that adding 0.3Mo to a Fe-0.1C-1.5Mn (%wt) induced a transformation stasis at 550-600 • C but not at 500 • C where Mo showed no effect on the plateau of transformation.…”

Section: Effect Of Mn and Mo On Ferrite Growth Kineticsmentioning

confidence: 65%

Use of Space-Resolved in-Situ High Energy X-ray Diffraction for the Characterization of the Compositional Dependence of the Austenite-to-Ferrite Transformation Kinetics in Steels

Benrabah

Landeghem

Bonnet

et al. 2019

QuBS

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In-situ high energy X-Ray diffraction (HEXRD) was used on compositionally graded steels to study the effect of substitutional elements on ferrite growth kinetics in Fe-C-X and Fe-C-X-Y systems. Two systems were selected to illustrate the applicability of the combinatorial approach in studying such transformations, Fe-C-Mn and Fe-C-Mn-Mo. Comparison between the measured ferrite growth kinetics using HEXRD and the predicted ones using Para-Equilibrium (PE) and Local Equilibrium with Negligible Partitioning (LENP) models indicates that the fractions reached at the stasis of transformation are lower than the predicted ones. Experiments indicated a deviation of measured kinetics from both PE and LENP models when increasing Mn and decreasing Mo (in Fe-C-Mn-Mo system). The large amount of data that can be obtained using this approach can be used for validating existing models describing ferrite growth kinetics.Quantum Beam Sci. 2019, 4, 1 2 of 17 is more complex than these limit cases. To explain this observation, it has been proposed that the interactions of solutes with the moving interface, while ignored in the two aforementioned models, lead to substantial dissipation of energy when the transformation occurs with negligible partitioning [14,15]. These interactions are known to exist because they lead to a compositional heterogeneity, or segregation, at the transformation interface that was experimentally measured using atom probe tomography (APT) or analytical transmission electron microscopy (TEM) [16][17][18]. The transport of this compositional heterogeneity during the transformation is the source of the additional dissipation termed solute drag (SD). Two different, but equivalent, formalisms were developed to express the amount of energy dissipated by solute drag [15,19]. This effect was integrated into a variety of models that displayed a better aptitude at predicting kinetics for broad ranges of composition and temperature in ternary systems [13,20,21]. One of the most notable characteristics of those models is their capability of describing the transition from PE to LENP transformation rates encountered in certain conditions. Attempts at generalizing those models to quaternary systems, containing two substitutional species, showed mixed results, which highlights the new questions they raise [22,23]. While they allow the description of complex interface behaviors, they require quantitative knowledge of thermodynamics in the interface, as a function of temperature and alloy composition [3].The effect of alloy composition can be tackled using a combinatorial approach on compositionally-graded alloys [24]. Such materials, usually made by joining dissimilar alloys subsequently heat-treated to promote interdiffusion, enable the exploration of a multitude of compositions, leading to maps of the composition-dependence of microstructures in a single step. This methodology is being actively developed in materials science [25], both from the viewpoint of microstructures [26] and from the viewpoint of related properties ...

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Direct measurement of carbon enrichment in the incomplete bainite transformation in Mo added low carbon steels

Cited by 67 publications

References 26 publications

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Effect of Mo Content on Microstructure and Property of Low-Carbon Bainitic Steels

Use of Space-Resolved in-Situ High Energy X-ray Diffraction for the Characterization of the Compositional Dependence of the Austenite-to-Ferrite Transformation Kinetics in Steels

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